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<p class="MsoNormal">Hello community,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">A while ago I sent a question about a problem with QMessageBox and message bar does not get updated during a long process.<o:p></o:p></p>
<p class="MsoNormal">In my example I create a script like this. <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">from qgis.PyQt import QtWidgets<o:p></o:p></p>
<p class="MsoNormal">message = "Wait to open the airspace project..."<o:p></o:p></p>
<p class="MsoNormal">msg = QtWidgets.QMessageBox()<o:p></o:p></p>
<p class="MsoNormal">msg.setText(message)<o:p></o:p></p>
<p class="MsoNormal">msg.show()<o:p></o:p></p>
<p class="MsoNormal">qgis.utils.iface.messageBar().pushMessage("Wait", message)<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">for i in range(1000):<o:p></o:p></p>
<p class="MsoNormal"> print(i)<o:p></o:p></p>
<p class="MsoNormal">qgis.utils.iface.messageBar().pushMessage("Done", "The process is done")<o:p></o:p></p>
<p class="MsoNormal">msg.setText("The process is done")<o:p></o:p></p>
<p class="MsoNormal">msg.show()<o:p></o:p></p>
<p class="MsoNormal">qgis.utils.iface.messageBar().pushMessage("Done", "The process is done"))<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">When I run the scrip in QGIS 2.18 the QMessageBox displays first the message "Wait to open the airspace project...". The same message is pushed to messageBar.<o:p></o:p></p>
<p class="MsoNormal">Then during the loop it displays the variable i.<o:p></o:p></p>
<p class="MsoNormal">At the end of the loop the QMessageBox displays the message "The process is done" which is also pushed to the messageBar.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">When I run the same scrip on QGIS 3 the QMessageBox is empty. The message "Wait to open the airspace project..." is not displayed by QMessageBox nor by messageBar.<o:p></o:p></p>
<p class="MsoNormal">The print inside the loop displays the I and when the loop is done the QMessageBox displays the message "The process is done".<o:p></o:p></p>
<p class="MsoNormal">The messageBar displays also the message "The process is done". And after a while it displays the initial message "Wait to open the airspace project..."<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I modified the scrip by adding QApplication.processEvents() inside the loop and now everything is fine.<o:p></o:p></p>
<p class="MsoNormal">It seems <span style="font-size:11.5pt;font-family:"Segoe UI",sans-serif;color:#232629;background:#F9F8F6">
QGIS3 no longer triggers this event loop and I have to do this explicitly by calling
</span>processEvents from QApplication.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><b><span style="background:yellow;mso-highlight:yellow">Why QGIS 3 needs to call QApplication.processEvents() and QGIS 2 does not need?</span><o:p></o:p></b></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thank you,<o:p></o:p></p>
<p class="MsoNormal">Marian<o:p></o:p></p>
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